Nutrient-laden wastewaters are typically treated to remove organic and inorganic nitrogen through specific processes. Examples of nutrient-laden wastewaters include leachates, or the liquids that drain (or “leach”) from landfills, or digester effluents; agricultural, industrial, and municipal wastewaters; and other similarly contaminated liquids.
The technologies in the prior art generally employ chemical and bacterial-based treatments, which, under specific aerobic or anoxic conditions, convert organic matter into ammonia (mineralization), ammonia into nitrite and nitrate (aerobic nitrification), and nitrite and nitrate into nitrogen gas (anoxic denitrification). These processes typically require, among other things, aerated and facultative lagoons, flocculation/clarification, activated sludge, sequencing batch reactors, membrane bio-reactors, reverse osmosis filtration, or other technologies.
The costs of each of these processes are related to the degree of treatment achieved, with nitrogen reduction typically being considered of high importance.
Previously, most U.S. state and federal environmental standards for effluent discharge ranged from 10 to 50 mg/L of Total Kjeldahl Nitrogen (TKN), which is calculated as the sum of organic nitrogen, ammonia (NH3) and ammonium (NH4+) in the effluent. Because TKN standards do not include nitrate and nitrite forms of inorganic nitrogen, the least expensive methods of treatment were based on the oxidation of organic nitrogen to ammonia followed by bacterial nitrification, or the conversion of ammonia to nitrite or nitrate. Under these standards, nitrification technology alone was usually sufficient without requiring the use of more expensive denitrification technologies.
New effluent discharge standards of the U.S. Environmental Protection Agency for nitrogen content are presently moving toward a range of 3 to 30 mg/L or lower. Moreover, these limits are defined as Total Nitrogen (TN) rather than the prior TKN standard, which requires more complex treatment approaches. These changing standards require not only the elimination of organic and inorganic nitrogen concentrations, but cause bacterial nitrification of ammonia to nitrite or nitrate to “qualify” no longer by itself as nitrogen removal because of the change in measurements from TKN to TN. Therefore, these fractions must now be either removed or further converted to elemental nitrogen through denitrification processes, or converted into biomass and then removed through other biological processes. Moreover, most air quality standards no longer allow for the free release of ammonia into the atmosphere.
U.S. and European sewage treatment operators are finding that leachates and similar wastewaters are difficult waste streams to treat due to very high ammonia nitrogen concentrations. Ammonia can be toxic to the bacterial colonies in traditional bacterial-based treatment systems. Furthermore, the bacterial treatment of ammonia requires a significant increase in aeration or oxygen demand resulting in greater treatment load, greater system capacity requirements, and significantly increased treatment operating costs.
In many types of wastewaters to be treated such as landfill leachate and anaerobic digester effluent, ammonia represents the majority fraction of the total nitrogen contained within the wastewater (often more than 80%) and organic nitrogen represents the remainder. In the case of landfill leachates, anaerobic digester effluent or other high ammonia wastewaters:                (1) These high ammonia wastewaters can cause problems in sewage plants that are so severe that the plants cannot meet their own discharge requirements.        (2) Some sewage plants have been forced to add expensive new treatment equipment to be able to accept such wastewaters.        (3) Sewage plants in several states have stopped accepting such wastewaters completely, or have set strict new standards for accepting their flows. This increases the need for cost effective on-site leachate treatment systems.        (4) Other sewage plants have raised the treatment fees that landfill operators must pay (up to 20 cents per gallon), and/or are requiring expensive pretreatment before they will accept such wastewaters.        (5) Successful lawsuits by environmental groups are forcing the states and the EPA to implement tough new water quality standards that directly affect leachate disposal.        (6) The U.S. is following in the path of the European Union, where leachate already is regulated so strictly that sewage plants cannot accept leachate at all, or expensive pretreatment of leachate (costing up to 18 cents per gallon) is legally required.        
It has recently been discovered that the presence of UV-absorbing compounds in some leachates can severely impact the effectiveness of ultraviolet light (UV) to provide disinfection in municipal wastewater treatment plants that treat such leachates. This can prevent such sewage treatment plants from meeting the EPA's goal to replace chlorine-based disinfection with the more environmentally safe UV disinfection process.
Unfortunately, most prior art processes do not attempt to recapture and recycle the valuable, energy-intensive, nitrogen products contained in wastewaters. In particular, early efforts to remove ammonia through degassing were more expensive or complex in comparison to simple nitrification processes and also were usually not concerned with preventing the release of ammonia into the atmosphere. Today, ammonia-rich emissions are no longer permitted due to environmental concerns.
Examples of such process in the prior art include the use of acidic solutions (as in U.S. Pat. Nos. and Patent Application Publication No. 4,308,049; 5,238,580; 7,270,796; and 2007/0297953), the evaporation or vaporization of leachate (as in U.S. Pat. Nos. 4,838,184; 5,542,482; 5,601,040; and 5,934,207); the recirculation of leachate within landfills (as in U.S. Pat. Nos. and Patent Application Publication No. 5,605,417; 6,024,513; 6,364,572; 6,398,958; and 2004/0191755); magneto-hydrodynamic, electrolytic and reverse osmosis processes (as in U.S. Pat. Nos. 4,678,582; 4,995,969; 6,428,697; and 7,517,456); and biological processes (as in U.S. Pat. Nos. 4,678,582 and 4,995,969).
U.S. Patent Application Publication No. 2009/0227003 to Blotsky et al. teaches methods and systems for biomass recycling and energy production that employ microbial digester units (aerobic and anaerobic) and algae production units. The Blotsky disclosure deals with the recycling of a biomass formed of solids and liquids than the recovery of ammonia from wastewaters and teaches microbial digester units that require extended time periods to perform the desired processes and possibly large surface areas to operate.
Therefore, there is a need for a method of treatment of ammonia-laden wastewaters that provides substantially nitrogen-free effluents at a low operational cost.